1. Field of the Invention
The present invention relates to an imaging system capable of being subjected to autoclave sterilization (high-pressure and high-temperature steam sterilization).
2. Description of Related Art
Imaging systems are used in optical endoscopes and electronic endoscopes. The imaging systems are capable of obtaining an optical image of a subject to form an endoscopic image, and displaying the image on a monitor or storing the image to an image recording device.
Such an imaging system includes an optical system for forming an optical image of a subject and an imaging device such as a CCD (charge coupled device) for obtaining the optical image formed through the optical system.
The imaging system requires the alignment between the optical system and the imaging device in order to obtain a favorable optical image of a subject. For the alignment between the optical system and the imaging device, the alignment therebetween is performed along the optical axis with respect to a focal length (focus adjustment) or the alignment therebetween is performed in the direction perpendicular to the optical axis.
Generally, the imaging system for endoscope needs cleaning and disinfecting after endoscopy. In addition, recently, the imaging system requires sterilization to prevent infections. The imaging system uses a low-cost sterilizing method for exposing an object to be sterilized in high-temperature and high-pressure steam for a predetermined period, the method being called autoclave sterilization. Accordingly, the optical system and the imaging device have to be hermetically sealed to allow the imaging system to exhibit resistance to the autoclave sterilization.
For example, Japanese Unexamined Patent Application Publication No. 2002-112956, to the same assignee as this application, discloses an imaging system for adjusting the focus of an optical system using magnetic connection.
PCT Japanese Translation Patent Publication No. WO 01/41631 A1, to the same assignee as this application, discloses an imaging system for adjusting a focus using an actuator in addition to the foregoing magnetic connection. Further, U.S. Pat. No. 5,490,015, to the same assignee as this application, discloses an imaging system for adjusting a focus using a piezoelectric element.
German Patent No. DE 19631840 A1 discloses an imaging system including a movable optical system in an airtight case. In the imaging system, a control section disposed in the housing is operated from the outside of a deformable wall region to vary the optical performance (a focal length) in airtight condition.
U.S. Pat. No. 5,225,941 discloses a driving device for an imaging system. In the driving device, an optical system is driven along the optical axis by frictional engagement with a shaft vibrated due to the expansion and contraction of a piezoelectric element.
U.S. Pat. No. 5,836,867 discloses a magnetic coupling assembly for an imaging system. In the assembly, the optical performance (a focal length) can be varied in airtight condition due to the magnetic coupling.